STMicroelectronics ISO808A-1

Overview

ISO808A-1 from STMicroelectronics is a galvanically isolated octal high-side power solid-state relay with SPI interface, designed for driving high inductive loads in industrial control systems. It features 8 independent channels, VCC operating range of 9.2–36 V, R_DS(on) = 0.125 Ω (TYP), per-channel current limit of 1 A (MIN), and integrated over-temperature protection with thermal independence per channel.

For engineers reviewing the ISO808A-1 datasheet, ISO808A-1 pinout, ISO808A-1 application, or ISO808A-1 equivalent, this device supports daisy-chained SPI configuration, provides open-drain FAULT/PGOOD diagnostics, delivers fast demagnetization (V_DEMAG = V_CC − 54 V), and meets IEC 61000-4-x immunity and UL1577/UL508 safety standards for PLC and NC machine deployments.

Technical Context

The ISO808A-1 implements dual isolated voltage domains: V_CC/GND_CC (process stage, up to 36 V) and V_DD/GNDDD (logic stage, 2.75–5.5 V), communicating via ST's proprietary isolation protocol. Each channel integrates independent junction over-temperature shutdown (T_JSD = 150–200 °C) and restart (T_JR = 160 °C), plus case-level thermal protection (T_CSD = 125–135 °C).

Its SPI interface operates up to 20 MHz with strict timing compliance (t_su(SS) = 80 ns, t_a(SDO) = 25 ns), supports daisy chaining, and includes watchdog timeout (t_WD = 272–400 μs) to force outputs OFF during logic-stage failure. Fault reporting occurs via OR-wired active-low FAULT pin covering OVT, communication errors, and invalid frame length.

Key Specifications

Pinout & Package

ISO808A-1 is packaged in PowerSO-36, a thermally enhanced surface-mount package with exposed V_CC tab (pin 36) and GND_CC tab (pin 19) for low-impedance thermal and power grounding. The 36-pin layout separates logic-side (V_DD, SPI, OUT_EN) and process-side (V_CC, OUT1–OUT8, GND_CC) terminals to maintain creepage/clearance ≥2.6 mm.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar galvanically isolated high-side driver applications.

Compared with TPL7407LA and ADUM3070, ISO808A-1 uniquely integrates eight isolated high-side switches, SPI control, diagnostics, and safety-certified insulation in a single PowerSO-36 package-reducing system-level component count by ≥12 parts and eliminating external isolation design effort.

Availability

ISO808A-1 is available at Aetrix Electronics and suitable for programmable logic controllers, industrial PC peripheral I/O, and numerical control machines requiring stable component supply, long-term lifecycle support, and certified functional safety compliance.

Supply support for ISO808A-1 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, delivering innovative silicon solutions for automotive, industrial, and power applications with emphasis on reliability and safety certification.

The ISO808A-1 belongs to ST's ISO8xx family of galvanically isolated high-side drivers, engineered specifically for industrial automation systems demanding functional safety, high noise immunity, and simplified SPI-based digital I/O expansion.

FAQ

What is the maximum continuous output current per channel for ISO808A-1?

The ISO808A-1 guarantees a minimum short-circuit current limit of 1 A per channel (ILIM(MIN) = 1 A), with typical R_DS(on) of 0.125 Ω enabling sustained 0.7–1.0 A operation depending on thermal conditions. Continuous current must be derated above 85 °C ambient per R_{th j-amb} = 16.9 °C/W (PowerSO-36) to maintain TJ < 150 °C.

How does the watchdog function interact with SPI communication?

The watchdog timer (t_WD = 272–400 μs) resets on every valid SPI frame transfer (8-bit boundary) or internal refresh signal. If no update occurs within t_WD, all outputs disable automatically-even if SS remains low. This ensures fail-safe behavior during MCU lockup or SPI bus contention without requiring software polling.

Can ISO808A-1 drive inductive loads without external flyback diodes?

Yes-the device incorporates fast demagnetization circuitry that clamps V_OUT to V_CC − 54 V (TYP) during turn-off, safely dissipating inductive energy internally. External diodes are optional but recommended for extreme energy levels (>2.11 J per channel) or to reduce junction temperature rise in high-duty-cycle applications.

What isolation certifications does ISO808A-1 meet?

ISO808A-1 complies with IEC 60747-17 (formerly VDE 0884-11) for reinforced galvanic isolation, achieves 1500 V_PEAK isolation test voltage, and holds UL1577 and UL508 certifications. It also meets IEC 61000-4-2 (ESD), -4-4 (EFT), -4-5 (surge), and -4-8 (power frequency magnetic field) immunity standards.